• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.393-403
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• 2022

Various studies suggest that the initial operating form of UAM, which is being presented as a solution to the urban traffic problem, will be similar to VTOL aircraft among current aircraft. In a form similar to determining the direction of the runway where fixed-wing aircraft take off and land, the vertiport where take-off and landing of VTOL aircraft takes place determines the flight direction of departure and arrival in consideration of the direction of the wind. Unlike areas where airports are generally built, in the case of downtown areas, it is expected that the characteristics of wind may continuously change depending on the environment of changing terrain or obstacles such as the construction of new buildings. In this study, long-term actual observation data for reviewing the take-off and landing directions at the city center where the location of the vertiport is expected are compared using a wind speed map, and the characteristics of the ground wind and the possibility of change in the direction of the predominant wind depending on the observation period and observation location confirmed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.175-176
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• 2023

1973년 최초로 서비스를 시작한 GPS는 전 세계 60억명 이상이 사용 중이며 거의 모든 사업에 큰 영향을 미치고 있으며, 자동차, 농업, 해양, 일반 안전, 레저활동, 지형공간정보, 항공, 금융, 통신 등 산업 전반에 걸쳐 경제적 이익이 약 1조4천억 달러에 이르는 글로벌 시스템이라 할 수 있다. 최근에는 미국의 GPS 뿐만 아니라 유럽, 러시아, 중국 등 세계 주요국들은 자국의 독자 위성항법시스템을 구축하고 있으며, PNT 정밀성 향상을 위한 위성항법보강시스템의 개발 또한 주요국 중심으로 이루어지고 있다. 4차산업기술의 발달로 인해 다양한 산업의 상용화와 대중화에 따라 PNT 정보의 고정밀, 고신뢰에 대한 수요도 급증하고 있으며, 이에 대한 응용기술 분야에 대한 시장도 급속하게 성장하고 있다. 우리나라에서도 KASS와 같은 위성항법보강시스템 구축을 추진하고 있으며, 향후 독자 위성항법시스템인 KPS의 개발도 진행중에 있다. 그러나 고도 23,000km에서 송출하는 위성신호의 전파교란·기만에 대한 취약성과, 도심지와 같은 위성신호 수신이 열악한 환경에서는 고정밀·고신뢰 PNT 정보를 제공하기가 현실적으로 어려운 실정이다. 이러한 GPS의 취약성을 보완하기 위해 지상기반의 PNT 정보제공 시스템 구축의 필요성이 증대되고 있으며, 전세계적으로 상호보완적 PNT 시스템의 구축·기술개발에 대한 연구가 다양하게 이루어지고 있다.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.61-66
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• 2023

In this study, we analyzed the flooded area around Samcheok Middle School caused by typhoons MAYSAK·HAISHEN in September 2020. To analyze the confluence of Samcheok Osipcheon, local stream Deungbongcheon, we utilized Iber, a two-dimensional hydraulic model. We simulated the water depth and flood extent based on the peak flows on September 3 and September 7, 2020, and the 80 year and 100 year frequency floods. The simulation results showed that the 80-year frequency flood and the 100-year frequency flood on September 7 were insignificantly different, but the maximum flow rate from September 3 to September 7 was significantly different at 401 m³/s, resulting in a difference of 0.8 m in water depth and 7.1 m² in flood area. In addition, the analysis that considered only the contour lines using contour lines predicted inundation of not only the Samcheok Middle School playground but also the building, confirming the need to apply DSM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.110-118
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• 2009

The tunnel structure is widely used for transportation in the mountain area. To reduce the duration of construction and thus the expense, a tunnel excavation is often performed simultaneously with a tunnel lining in in-situ. However, cracking of the tunnel lining may occur arising from the vibrating impact in the excavation process. The present study concerns the role of steel fiber and nylon fibers in tunnel lining concrete to reduce the vibrating impact. As a result it was found that both the nylon fiber and steel fiber improved the durability and physical properties of concrete.

• Journal of Advanced Navigation Technology
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• v.28 no.4
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• pp.393-399
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• 2024

The digital map computer for advanced air vehicles (AAV) must be high-performance, lightweight, portable, and modular. It should receive data on terrain, weather, and obstacles from external modules to display digital maps accurately. This necessitates robust communication capabilities with external devices via an Ethernet interface and the ability to output digital map visuals clearly through an high-defintion multimedia Interface (HDMI) or digital visual interface (DVI) interface. This paper presents the design of both hardware and software architecture that fulfills these critical requirements for an AAV digital map system. Additionally, it establishes the minimum specifications needed and verifies the suitability of the designed digital map computer through rigorous performance measurements and testing. By ensuring these standards, the digital map computer can reliably support the complex navigational needs of AAV, enhancing operational efficiency and safety.

• Journal of the Korea Society of Computer and Information
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• v.29 no.10
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• pp.1-9
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• 2024

In this paper, we propose a comparative analysis to evaluate the impact of activation functions and attention mechanisms on the performance of time-series models for Mars meteorological data. Mars meteorological data are nonlinear and irregular due to low atmospheric density, rapid temperature variations, and complex terrain. We use long short-term memory (LSTM), bidirectional LSTM (BiLSTM), gated recurrent unit (GRU), and bidirectional GRU (BiGRU) architectures to evaluate the effectiveness of different activation functions and attention mechanisms. The activation functions tested include rectified linear unit (ReLU), leaky ReLU, exponential linear unit (ELU), Gaussian error linear unit (GELU), Swish, and scaled ELU (SELU), and model performance was measured using mean absolute error (MAE) and root mean square error (RMSE) metrics. Our results show that the integration of attentional mechanisms improves both MAE and RMSE, with Swish and ReLU achieving the best performance for minimum temperature prediction. Conversely, GELU and ELU were less effective for pressure prediction. These results highlight the critical role of selecting appropriate activation functions and attention mechanisms in improving model accuracy for complex time-series forecasting.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.895-902
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• 2024

AI requires learning, and learning requires data. Some data is copyright-free, such as mountains, oceans, and terrain, while others are restricted by various laws, such as privacy and copyright laws. This thesis investigates how data subjects can voluntarily consent and participate in the collection, utilization, and distribution of their data, overcoming legal restrictions. We design a system that creates specific spaces in public places, engages businesses to define the data needed for learning, and rewards citizens for voluntarily participating in the collection of Multimodal MyData in specific spaces. In addition, a system that enables authentication, distribution, and sale/resale of generated data in connection with the government's MyData platform will be implemented. If this is led by the government, it will be possible to collect data for learning in a new way without legal sanctions for each learning domain, which will further revitalize the development and utilization of AI technology.

• Korean Journal of Soil Science and Fertilizer
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• v.10 no.3
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• pp.189-201
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• 1977

Some of basic aspects of soil potassium with special reference to soil physical properties were discussed. Data in the Official Soil Series Description(Korea) was analyzed according to soil type, land form, and soil texture to find soil potassium status which may explain different response to potassium application. Exchangeable potassium contents decreased with soil depth irrespective of soil type, land form and soil texture. Change in degree of potassium saturation within soil profile was not so clear as exchangeable potassium but the degree of potassium saturation of A horizon was highest among soil horizon. Soils of terrace and mountain foot slope showed high values both in exchangeable potassium and degree of potassium sauration and only these two soils were classified as soils having exchangeable potassium higher than 0.3 meq per 100g of soil and degree of potassium saturation higher than 5.0%. Exchangeable potassium of fine loamy and fine clayey soils is higher than 0.3 meq per 100g of soil but degree of potassium saturation is lower than 4.0%. Degree of potassium saturation of sandy soils exceeds 5.0% but exchangeable potassium is very low. Soils of rolling, hilly, unmatured and alpine land soils have lower exchangeable potassium and show lower degree of potassium saturation. The highest distribution of exchangeable potassium content irrespective of soil horizons was shown in the range of 0.1-0.2 meq per 100g of soil. The highest distribution of degree of potassium saturation was in the range of 2.0-3.0% in A horizon and 1.0-2.0% in B and C horizons. Of the soil series concerned in this analysis, 27.3% in A horizon, 11.1% in B horizon and 4.0% in C horizon had exchangeable potassium higher than 0.3 meq per 100g of soil and 18.0% in A horizon, 6.3% in B horizon, and 4.1% in C horizon showed degree of potassium saturation higher than 5.0%. The low response of potassium application only to soils in terrace and mountain foot slope may be resulted from the high exchangeable potassium content and high degree of potassium saturation. It is concluded that a great response of potassium application to soils is expected especially in dry season.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.1
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• pp.20-35
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• 2002

We studied the fishing ground of a yellowtail and oceanographic conditions around Chujado and Marado around Jeju Island from autumn to winter. Also we investigate the forming mechanism of fishing ground around Marado, which shows the best catch of yellowtail near Jeju island. The obtained results are summarized as follow ; 1. When the high temperature water about 15.0∼19.0 in depth of 50m distributed around Chujado and Marado, the fishing ground of Yellowtail is shows a good catch. On the contrary, when the low temperature water about 11.0∼14.0 is shows a poor catch. 2. Fishing grounds of yellowtail by handline fishing are formed with a school of Yellowtail migrating southward from the coastal sea of Korea and slaying around Marado to winter and spawn due to following factors. Firstly, a front of temperature and salinity is formed between inshore water and oceanic water around Marado. Secondly, small-size eddies and excellent horizontal and vortical mix which is created by strong tide and geographical features including irregular underwater ground and an isolated island. An abundant school of yellow tails stays in front of the tide where a good fishing ground was made.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.4
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• pp.289-293
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• 2008

Reproduction of the goby fish Periophthalmus magnuspinnatus was examined using 298 specimens collected from April to October 2005 in a mud flat of Suncheon Bay, Korea. Specimens ranged in body length(BL) from 1.3 to 9.1 cm. The gonadosomatic index(GSI) of females was highest in June and decreased until August. The hepatosomatic index(HSI) and fatness index of females were high in April and then decreased to nadirs in July. Spawning season lated from April to August and the ratio of females to males did not significantly differ($x^2$-test, p>0.05). The first spawning length was 4.5 cm BL, and the size of 50% maturity was estimated at 4.98 cm BL. Fecundity(F) ranged from 1,316 to 4,768 eggs, and the relationship between F and BL was estimated as $F=0.1562BL^{1.4068}(R^2=0.59)$.